Skip to main content

Class 11 Chemistry s-Block Elements NCERT Theory: Group 1 and Group 2 Properties, Reactions, Trends, Compounds, and Biological Importance


The s-Block Element – Class 11 NCERT Theory


Introduction:



The s-block elements include Group 1 (alkali metals) and Group 2 (alkaline earth metals).


These elements have their valence electron(s) in the s-orbital.


General electronic configuration:


Group 1: ns¹


Group 2: ns²


Group 1 Elements – Alkali Metals


Elements: Li, Na, K, Rb, Cs, Fr


Soft, silvery-white metals


Low melting and boiling points


Low density (Li, Na float on water)


Highly reactive, especially with water and air


Stored under kerosene



Physical Properties:


Large atomic and ionic size


Low ionization enthalpy


Good conductors of heat and electricity


Flame test: Li – crimson red, Na – golden yellow, K – violet



Chemical Properties:


Reactivity with air: Forms oxides, peroxides, or superoxides


Reactivity with water: Produces strong base (MOH) and H₂ gas



\ce{2Na + 2H2O -> 2NaOH + H2}


Important Compounds of Sodium:


NaCl – Common salt


NaOH – Strong base, caustic soda


Na2CO3.10H2O – Washing soda


NaHCO3 – Baking soda


Na2SO4.10H2O – Glauber’s salt




---


Group 2 Elements – Alkaline Earth Metals


Elements: Be, Mg, Ca, Sr, Ba, Ra


Harder than alkali metals


Higher melting points and densities


Less reactive than Group 1 but reactivity increases down the group


Flame test: Ca – brick red, Sr – crimson, Ba – apple green



Physical Properties:


Smaller atomic and ionic sizes than Group 1


Higher ionization enthalpies


Form +2 oxidation state


Less electropositive than alkali metals



Chemical Properties:


Reaction with oxygen: Forms oxides (MO), some form peroxides (BaO₂)


Reaction with water:


Be does not react


Mg reacts slowly


Ca, Sr, Ba react readily forming hydroxides




\ce{Ca + 2H2O -> Ca(OH)2 + H2}


Reaction with acids: Liberates H₂ gas



Important Compounds of Calcium:


CaO (Quick lime) – Basic oxide, used in cement


Ca(OH)₂ (Slaked lime) – Used in whitewashing


CaCO₃ (Limestone) – Used in glass, cement, etc.


CaSO₄·½H₂O (Plaster of Paris) – Used in casts and building


CaCl₂ – Moisture absorbent




---


Anomalous Behavior of Lithium and Beryllium:


Due to small size, high ionization energy, and high polarizing power


Lithium:


Forms covalent compounds


Li₂CO₃ decomposes easily


LiOH is a weak base


Shows diagonal relationship with Mg



Beryllium:


Amphoteric oxide and hydroxide


Forms covalent halides


Does not react with water





---


Diagonal Relationship:


Li ↔ Mg and Be ↔ Al


Due to similar charge/radius ratio and electronegativity




---


Trends in s-Block Elements:


Property Trend (Down the Group)


Atomic size Increases

Ionization enthalpy Decreases

Electropositivity Increases

Melting/boiling point Decreases (Group 1)

Reactivity Increases

Thermal stability Increases (carbonates)




---


Biological Importance:


Na⁺ and K⁺: Maintain osmotic balance, nerve transmission


Mg²⁺: Present in chlorophyll, enzyme activator


Ca²⁺: Bones, teeth, blood clotting, muscle function




"This Content Sponsored by Buymote Shopping app


BuyMote E-Shopping Application is One of the Online Shopping App


Now Available on Play Store & App Store (Buymote E-Shopping)


Click Below Link and Install Application: https://buymote.shop/links/0f5993744a9213079a6b53e8


Sponsor Content: #buymote #buymoteeshopping #buymoteonline #buymoteshopping #buymoteapplication"



Comments

Post a Comment

Popular posts from this blog

"Unlocking Chemical Bonding: Valence Bond Theory and Its Applications in Chemistry and Beyond"

 *Valence Bond Theory: A Fundamental Concept in Chemistry* Valence Bond (VB) theory is a fundamental concept in chemistry that explains the formation of chemical bonds between atoms. Developed by Walter Heitler and Fritz London in 1927, VB theory provides a simple and intuitive understanding of chemical bonding. *Key Principles:* 1. *Atomic Orbitals:* VB theory assumes that atomic orbitals are the fundamental building blocks of chemical bonds. 2. *Overlap of Atomic Orbitals:* Chemical bonds form when atomic orbitals from different atoms overlap. 3. *Hybridization:* Atomic orbitals can hybridize to form new hybrid orbitals that are more suitable for bonding. *Types of Hybridization:* 1. *sp3 Hybridization:* One s orbital and three p orbitals mix to form four equivalent sp3 hybrid orbitals. 2. *sp2 Hybridization:* One s orbital and two p orbitals mix to form three equivalent sp2 hybrid orbitals. 3. *sp Hybridization:* One s orbital and one p orbital mix to form two equivalent sp hybr...
Post a Comment
Read more

p-Block Elements Class 11 Chemistry NCERT Theory – Group 13 and 14 Complete Notes for NEET and CBSE Students

🧪 The p-Block Elements – Class 11 Chemistry NCERT Theory Explanation 📘 Introduction to p-Block Elements The p-block elements are those in which the last electron enters the p-orbital of the outermost shell. They are located on the right side of the periodic table and include Groups 13 to 18. In Class 11, we mainly study Group 13 (Boron family) and Group 14 (Carbon family). 🧱 Group 13 Elements – The Boron Family 🧬 Elements: Boron (B), Aluminium (Al), Gallium (Ga), Indium (In), Thallium (Tl) ⚛️ Electronic Configuration: General: ns² np¹ 📈 Physical Properties: Boron is a metalloid, while others are metals. Melting and boiling points decrease down the group. Boron is hard, while aluminium is light and malleable. 🔬 Chemical Properties: Oxidation State: +3 is common; Tl also shows +1 (inert pair effect). Reactivity with acids and bases: Boron does not react with dilute acids. Aluminium reacts and liberates hydrogen gas. ⚗️ Important Compounds of Boron: 1. Borax (Na₂B₄O₇·10H₂O): Used in...
Post a Comment
Read more

"SN1 Mechanism: A Two-Step Nucleophilic Substitution Reaction with Carbocation Intermediate Formation and Nucleophilic Attack"

 The SN1 mechanism is a type of nucleophilic substitution reaction that involves a two-step process: Step 1: Formation of a Carbocation Intermediate 1. *Leaving group departure*: The leaving group (such as a halide ion) departs, forming a carbocation intermediate. 2. *Carbocation formation*: The carbocation intermediate is formed, which is a planar, sp2-hybridized carbon atom. Step 2: Nucleophilic Attack 1. *Nucleophile approach*: A nucleophile (such as a water molecule or an alkoxide ion) approaches the carbocation intermediate. 2. *Bond formation*: The nucleophile forms a bond with the carbocation intermediate, resulting in the formation of the product. Characteristics of SN1 Mechanism: 1. *Rate-determining step*: The rate-determining step is the formation of the carbocation intermediate (Step 1). 2. *Stereochemistry*: The SN1 mechanism results in the loss of stereochemistry, as the carbocation intermediate can be attacked by the nucleophile from either side. 3. *Rearrangement*: ...
Post a Comment
Read more